Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4492923.

A bunch of our vinyl fence pickets are missing the trapezoidal top. I didn't have any luck buying replacements that fit (without have to grind the plastic tabs down).

The internal dimensions on the picket part (hollow area) should be 18mm x 71mm for this to fit.

You'll want to print in something like ABS or PETG so the sun doesn't ruin it. Print "upside-down."